1. Field of the Invention
This invention relates to detecting entity changes and more particularly relates to detecting entity changes in a storage area network environment.
2. Description of the Related Art
Storage area networks (SAN) are increasingly popular for storing large quantities for data. A SAN includes multiple entities such as hosts, storage subsystems, host bus adapters, storage volumes, storage pools, etc., as well as relationships between them such as links. In this document, the term “entity” is used to refer to both entities and relationships. The state of these entities is always in flux. Entities may be created or deleted, or the attributes of the entities change in response to events in a SAN.
A change to an entity is referred to herein as an event. Entities have one or more attributes such as storage capacity, available communication channels, read and/or write latency, and the like. An entity attribute change may be an event. For example, the addition of a hard disk drive to a storage subsystem comprising a plurality of hard disk drives may increase the storage capacity of the storage subsystem, changing an attribute of the storage subsystem entity.
An event may also include the creation or deletion of an entity within the SAN. Creation as used herein refers to an entity beginning communications with the SAN while deletion as used herein refers to an entity terminating communications with the SAN. As used herein, an entity that communicates within the SAN is referred to as being visible within the SAN. An event may include an entity previously visible within the SAN becoming no longer visible within the SAN. In one embodiment, the entity is no longer visible within the SAN if the entity cannot be communicated with. Alternatively, the entity is no longer visible within the SAN if the entity is not present within the SAN.
A system managing a SAN requires an efficient mechanism to process events in the SAN and inform an administrator about the changes to the entities in the SAN. It is particularly important to inform the administrator about changes to entities in the SAN that are of the interest to the administrator. For example, a SAN might include a million or more entities, but the administrator might be interested in only a subset of entities that are critical to the operation of a data center.
In the past, entities have generated raw reports of events and communicated the reports directly to a console used by the administrator. The administrator may filter the reports, so that only entities of interest are displayed. Unfortunately, duplicate reports relating to a single event are common, making it difficult for the administrator to identify critical events.
An entity may also periodically communicate a report to the administrator detailing the entity's status. The administrator may have difficulty identifying changes in the entity's status from the plurality of status reports that are received. As a result, critical changes to the entity and/or the entity's attributes may go unnoticed.
Management systems have attempted to make events more visible to the administrator by comparing status reports with a baseline status report. Unfortunately, meaningful baselines are not always available for the entities of a SAN system. As a result, many events are unrecognized by the administrator even when status reports are compared with baseline reports.
In addition, some events may not result in the generation of reports. For example, if an entity is deleted or is no longer visible within the SAN, the entity may not generate and/or communicate a report to the administrator. As a result, many events may not be reported at all to the administrator. Similarly, the creation of an entity within the SAN such as the addition of a host may not generate a report.
From the foregoing discussion, it should be apparent that a need exists for an apparatus, system, and method that detects entity changes in a SAN. Beneficially, such an apparatus, system, and method would provide useful management information to the SAN administrator.